India: Southwest monsoon withdrawal, Northeast monsoon onset likely this week

The Indian Meteorological Department (IMD) has said that the conditions are favourable for the withdrawal of the southwest monsoon from the entire country by Thursday (October 16). Typically active between June and September, the southwest monsoon brings in the vast majority of India's annual rainfall. Likewise, the Northeast monsoon which brings rains across parts of southern India is expected to set in around Thursday. Also known as the retreating monsoon, the Northeast monsoon is the second major rainfall season in India, and is crucial for large parts of Tamil Nadu, Andhra Pradesh, Puducherry.

The two are related in such a way that the Northeast monsoon occurs when the southwest monsoon withdrawal, and the wind direction reverses. The Northeast monsoon sets in around mid-October and goes on till mid-December. The Northeast monsoon caters for about 50% or more of the annual rainfall in Tamil Nadu and coastal Andhra Pradesh. This season is known for cyclonic storms or weather systems that form in the Bay of Bengal, which can lead to very heavy rainfall and potential flooding in parts of Tamil Nadu and coastal Andhra Pradesh. These rains are also crucial for recharging the water table and the reservoirs.

Meanwhile, there is an Upper Air Cyclonic Circulation over the Southwest Bay of Bengal and adjoining and Indian Equatorial Ocean up to 3.1 km above mean sea level. It is likely to move west-northwestwards towards Kanyakumari, the Indian mainland's southernmost tip. Under its influence, a Low Pressure Area is likely to form over Southeast Arabian Sea and adjoining Lakshadweep area off Kerala-south Karnataka coasts around 19th October. A low pressure area is associated with storm weather, rainfall, gusty winds.

For the next four days, IMD has predicted heavy rains for several districts across Tamil Nadu. Owing to gusty winds during this period, fishermen have been advised to avoid venturing out along the southern Tamil Nadu coastal regions and the Kerala coastal regions.